Communication between divers underwater is critical for safety and contributes significantly to the enjoyment of underwater activities, whether for sport or business. In the past, visual communication has been made through hand gestures, slate boards or signal lights. However, it is often difficult or impossible to attract another diver's attention underwater unless that diver is nearby and looking in the direction of the diver requiring attention. Use of a slate board for writing messages underwater is subject to misunderstanding through poor visibility or poor penmanship. It is also awkward and time consuming, requiring the diver to employ both hands. Striking an air tank with a knife or other metal object to produce a clanking noise is another common form of communication, but is cumbersome, time consuming in an emergency and does not convey any specific message.
Several attempts have been made to overcome these shortcomings of prior communication procedures. One example is U.S. Pat. No. 3,909,773 issued to Saltzer. This patent discloses the use of a wrist carried keyboard control unit for use by a diver for two-way communication with a surface vessel. Prerecorded messages can be stored in a read only memory within the control unit. The diver can operate the keyboard to send the prerecorded message through a narrow band transmission to the surface vessel. The diver is also capable of sending a nonrecorded message by typing the message into the keyboard. The control unit can receive a message from the surface and retains the message in a memory until the diver can read the message.
However, a need exists for a device for underwater communication between divers which is self-powered, self-contained and does not constrain the mobility or motion of the diver. In addition, since a diver is impaired from speaking, but not from hearing or seeing over short distances underwater, a need exists for a device which permits communication through underwater acoustic speech transmission and visual transmission.